1. Field of the Invention
The present invention relates to a simulation apparatus of a wire electric discharge machine and, in particular, to a simulation apparatus of a wire electric discharge machine having the function of determining welding positions, a welding number, or the like of a core according to an environmental condition such as a shape of the core.
2. Description of the Related Art
FIG. 9 is a top view of a workpiece machined by a wire electric discharge machine.
The wire electric discharge machine starts the machining of a workpiece 3 from a machining start hole 31. A machining path through which a wire electrode (not shown) passes is indicated by a machining groove 32. A machining method with a conventional wire electric discharge machine causes problems when a core 33 is cut out; for example, the cut-out core 33 and the wire electrode contact each other to cause disconnection of the wire electrode, or the wire electrode and the workpiece 3 are short-circuited via the core 33 to cause a scratch on the core 33 and the workpiece 3.
In view of the above problems, there has been employed a technology in which welding parts 34 to weld the core 33 and the workpiece 3 to each other using a molten material made by melting the wire electrode are formed during machining of the workpiece 3 at some parts of the machining groove 32 formed on the machining path, thereby preventing the core 33 from dropping upon completion of the machining. As a technology for welding the core 33 to the workpiece 3 so as to prevent the core 33 generated through electric discharge machining from dropping, Japanese Patent Application Laid-open No. 2014-024132 discloses a technology for correcting a machining program so as to evenly arrange welding parts 34 and welding suspension parts 35 on the machining path, in accordance with a shape of a core 33.
When this conventional technology is employed, it is necessary to calculate positions and lengths of the welding parts 34 on the machining path, intervals between the welding parts 34 (lengths of the welding suspension parts 35), and the number of the welding parts 34 provided on the machining path, in accordance with the shape of the core 33, and create a welding program according to the calculation results.
For example, the core 33 shown in FIG. 10A and the core 33 shown in FIG. 10B are different in shape, therefore in order to hold the respective cores 33 in a well-balanced fashion and enable their removal with reasonable force, positions and lengths of the welding parts 34, intervals between the welding parts 34 (lengths of the welding suspension parts 35), and the number of the welding parts 34 on the machining paths must be designed differently for each core 33. That is to say, it is necessary to generate different welding programs so as to correspond to the respective cores 33 having the respective shapes shown in FIG. 10A and FIG. 10B.
In order to calculate the above values (positions and lengths of the welding parts 34, lengths of the welding suspension parts 35, and the number of the welding parts 34) so as to correspond to the shapes of the cores 33, it is necessary to consider differences in balance (centroid or the like), retention ability, dropping easiness (ease with which to drop the cores), and machining easiness such that these correspond to the shapes of the cores 33. Here, consideration is given to retention ability since the cores 33 cannot be supported when the lengths or number of the welding parts 34 is too small. Dropping easiness is taken into account because when the welding parts 34 are poorly positioned or when the lengths or number of the welding parts 34 is excessive, extra force is needed to drop the cores 33 from the workpieces 3. Further, consideration is given to machining easiness because an excessive number of the welding parts 34 leads to increased number of operations to modify machining conditions during wire electric discharge machining, which consequently lengthen the machining time.
In this respect, the effect of the above technology disclosed in Japanese Patent Application Laid-open No. 2014-024132 is limited to evenly arranging the positions and lengths of the welding parts 34 on the machining path, and does not take account of the shape of the core 33 when calculating the positions, lengths, or the like of the welding parts 34. Therefore, for certain shapes of cores to be formed by electric discharge machining, the balance, retention ability, dropping easiness, and machining easiness may not be suitable.